This is not a unique event. The Buccaneers have made it clear that they're very interested in drafting quarterbacks, attended Blake Bortles pro day, have met with Jimmy Garoppolo and shown interest in Brett Smith. The Bucs are gearing up to add another quarterback in the draft -- the question is just which one.
Lovie Smith has repeatedly emphasized quarterback mobility in his comments, but I'm not sure Manziel's free-wheeling style fits Jeff Tedford's more controlling system. Manziel thrives on improvisation (though that is far from the only aspect to his game), and Tedford is all about providing answers for quarterbacks within structure. Perhaps that changes now that he's in the NFL, but I doubt it.
Still, there's more to the team's quarterback evaluation than just Jeff Tedford, and Lovie Smith's not about to bind his future to a quarterback he doesn't trust, simply because his offensive coordinator likes him.
Regardless, this isn't really news. The Bucs will presumably meet with all of the top quarterbacks, and they've at least shown interest in a few of the quarterbacks who are generally projected to go in the later rounds. Is this just the team doing due diligence, or being genuinely interested in Manziel as a possible quarterback at the future? In the end that may be a moot point: the Texas A&M prospect may not even be available at the seventh overall pick.